1. Field of the Invention
This invention relates to conduit cleaners of the type employing a rotary cutting blade and, more particularly, to a cutting blade assembly for such a conduit cleaner which has cutting blades positively attached thereto in such a manner as to facilitate assembly and disassembly of the cutting blade assembly.
2. Background Art
Fluid powered conduit cleaners are well known in the art. An exemplary conduit cleaner is disclosed in U.S. Pat. No. 3,740,785, to Latall. High pressure water delivered to the Latall unit rotates a cutting blade assembly at the leading portion thereof and simultaneously exhausts angularly in a trailing direction through jets so as to impinge upon a conduit wall. This action causes propulsion of the unit and at the same time breaks up foreign matter within the conduit and scours the conduit wall, as to break loose deposits of fat, paraffin, and the like. A skid assembly guides the entire unit in translation against the conduit.
A typical cutting blade assembly has a hub mounted to a rotary shaft and a cutting blade, in the form of a flexible strip, that is wrapped in a substantially circular pattern. The blade is anchored to the hub by directing the free end of the blade radially through the center of the hub. This has generally been recognized as a preferred way of securely holding the blade in place.
The difficulty with the aforesaid arrangement is that the blade anchoring end obstructs the center of the hub so as to prohibit axial passage through the hub of a fastener, as would permit such a fastener to be accessed from the front of the unit. Instead, the hub is elongated to define an axially extending anchoring portion which accepts a fastener that is directed through aligned radial bores in the hub and shaft. This construction has several drawbacks which designers have, to this stage, been unable to overcome.
First of all, if more than one blade is anchored to the hub in the above manner, the penetrated hub becomes inherently weaker, and thus prone to failure.
A more serious problem is that of accessing the fastener/bolt that is used to attach the hub to the shaft. The bolt resides within a narrow space axially between the cutting blade and the motor housing and skid assembly. By lengthening the hub to facilitate access to this mounting bolt, the overall length of the unit is necessarily increased, which is undesirable. At the same time, this lengthening may weaken the hub which again makes it more prone to failure when subjected to normal operating torques.